ST LOUIS (AFP) - Police from the US city of St Louis shot dead another suspect on Tuesday a short distance from a suburb that is already the scene of protests over last week's killing of an unarmed teenager.

St Louis police chief Sam Dotson said in a tweet that officers had responded to a call and found an apparently agitated man, armed with a knife who yelled "kill me now" and approached the patrol.

In a tweet from his own account retweeted by his force, Dotson said: "Officers gave suspect verbal commands. Officers feared for their safety and both officers fired their weapons. Suspect is deceased."

The world's media descended on the street where the latest police shooting took place, dozens of reporters having been in the nearby suburb of Ferguson covering the ongoing unrest.

Onlookers gathered at the yellow incident tape sealing off the scene of Tuesday's shooting outside a convenience store in St Louis, some of them chanting the slogan of the protests: "Hands up, don't shoot."

On Aug 9, a white officer in Ferguson shot and killed an 18-year-old unarmed black student, triggering more than a week of sometimes violent protests against heavy-handed police tactics.